Incandescent lamp with wall bumper

ABSTRACT

A single-ended lamp, having a pinch seal at one end and a tipped-off residue of an exhaust tube at the other end, has a wall bumper, located near the envelope end containing the tippedoff residue, which comprises a large diameter turn of wire and several small diameter turns of wire connected to a power lead. A method of manufacturing a lamp which utilizes a wall bumper to prevent mount movement during pinch sealing and which also permits the envelope to be effectively flushed with an inert gas thereby reducing lamp part oxidation during pinch sealing.

United States Patent Danko Aug. 5, 1975 [54] INCANDESCENT LAMP WITH WALL 3,748,519 7/1973 Martin et a]. 313/279 BUMPER 3,760,217 9/1973 Martin et al... 313/279 3,784,865 1/1974 Shanks 313/279 [75] Inventor: George K. Danko, Bedford Heights,

Ohm Primary Examiner-Saxfield Chatmon, Jr. [73] Assignee; General Electric Com any, Attorney, Agent, or Firm-Ernest W. Legree;

Schenectady, NY. Lawrence R. Kempton; Frank L. Neuhauser [22] Filed: Feb. 22, 1974 [57] ABSTRACT 211 App]. No.2 444,747

A single-ended lamp, having a pinch seal at one end and a tipped-off residue of an exhaust tube at the [52] US. Cl. 313/271; 313/279; 313/284, Othelend has a n bumper located near the enve 3 l3/286 lope end containing the tipped-off residue, which [51] Holj 1/88; 3 19/42; Holk 1/18 comprises a large diameter turn of wire and several [58] Field of Search 313/279, 284, 286, 271 Small diameter turns of Wire connected to a power lead. A method of manufacturing a lamp which uti- [56] References Cited lizes a wall bumper to prevent mount movement dur- UNITED STATES PATENTS ing pinch sealing and which also permits the envelope 3,300,675 1/1967 Deshaw 313/284 X to be effectively flushed with an inert gas thereby 3,392,299 7/1968 Kern 313/279 ducing lamp part oxidation during pinch sealing. 3,496,403 2/1970 Palermo et al..... 313 279 X 3,696,265 10 1972 Martin et =11. 313 279 2 Clams, 4 Drawing Figures ill] INCANDESCENT LAMP WITH WALL BUMPER BACKGROUND or THE lNVENTION l. Field of the Invention The invention relates to incandescent lamps and a method of manufacturing an incandescent'lamp. More particularly, the invention relates to a lamp containing a wall bumper which prevents mount movement during pinch sealing and a method of manufacturing a lamp which uses an envelope having small inside length to inside diameter ratio. i

2. Description of the Prior Art I In manufacturing lamps containing pinch seals whic are made at high temperatures, it-is necessary to flush the envelope with an inert gas, such as nitrogen, to prevent oxidation of the lamp parts. Oxidation takes place when oxygen is present either as an element or a constituent of air in the envelope at elevated temperatures caused by the fires used for pinch sealing. Normally, nitrogen is flowed into the envelope through a port or hose connection to an exhaust tube. However, in lamps which have a small inside length to inside diameter ratio, a great degree of turbulence is encountered when the jet of flush gas contacts the mount-pin and seal area. With this turbulence, the flush gas is not always effective in preventing lamp part oxidation becauseair either remains inside the envelopeor is drawn in by the turbulent gas flow. 1 i

This problem can be aggravated by the presence of a support member located such that a portion of the support extends into the exhaust tube. The reason for a part of the support extending into theexhaust tube is to prevent mount movement during pinch sealing. Without a support or restraint, .the'mount would shift as the molten envelope material flows during=the pinch sealing operation.

Another problem encountered withprior art lamps is movement of the filament caused by vibration during shipping. ,1

SUMMARY OF THE INVENTION It is therefore an object of the invention to. manufacture a lamp which is so constructed that it minimizes the effect of vibration on the coiLand mount structure while the lamp is in transit. A further object of the invention is to provide a mount structure with a wall bumper such that the mount will not shift during the pinch sealing process. Yet another object of. the invention is to provide a mount structurewhich doesrnot interfere with the flow of flush gas. Still another object of the invention is to devise a methodof manufacturing single-ended lamps, having small inside length to inside diameter ratio, without oxidizing lamp parts during the pinch sealing operation. 1

The objects of the invention are accomplished by providing a mount structure for a single-ended lamp with a wall bumper. In the process or method of manu facturing a single-ended lamp, a mount comprising two lead wires and a filament is held in a mount pin. Since many times foils or foliated portions are part of the lead wires and since accurate filament alignment is important, a technique must be provided to prevent mount movement when the hot molten quartz or glass begins to flow around the thin foil portions.

It has been found that a circular shaped coil or turn ofwire, having a large outside diameter, slightly smaller than the inside diameter of the envelope, effectively prevents the mount and in turn the coil from shifting to anyappreciable degree during the pinch sealing process. In addition to the larger circular portion of the wall bumper, it has a smaller diameter portion of approximately five turns which are screwed onto one of the lead wires.

Since the wall bumper relies upon the envelope wall,

--it is not necessary to protrude into the exhaust tube to obtain mount stability. Accordingly, a flush needle can be inserted into the lamp to effectively flush out all air and oxygen thereby preventing lamp part oxidation a the high pinch sealing temperatures.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front elevation view of an unsealed singleended lamp of the prior art;

' FIG. 2 is a front elevation view of an unsealed singleended lamp utilizing the invention;

FIG; 3 is an elevation view of a finished lamp embodying the invention; and

FIG 4 is an enlarged perspective view of the wall bumper of the invention.

-- DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIGS. 1 and 2 of the drawings, unsealed single-ended lamps of both the invention and prior art are therein illustrated. Lamp 10 of the prior art is comprised of envelope 11, power conductors 12 and 13, spud 14 and exhaust tube 15. Prior to pinch sealing, a hose 16 which is connected at its other end to a pressurized source of gas is connected directly to the exhaust tube 15.

A gas, usually nitrogen, is flowed through the hose into the exhaust tube and down into the envelope. The gas exits through the open bottom portion 17 of the envelope ostensibly removing all air and oxygen which might react with the internal lamp parts. As bottom portion 17 is heated prior to sealing, it becomes increasingly important for the lamp to be cleansed or flushed of all oxygen and air.

7 In lamps such as those illustrated in FIGS. 1, 2 and 3, the possibility of turbulence being created, either by the gas hitting the mount holder at too great a velocity or by hitting the glass or quartz as the pinch seal is being formed, is greatly increased by the fact that the bottom of the envelope is comparatively close to the endof the exhaust tip. In other words, the inside length to inside diameter ratio of this particular lamp is relatively small. 3.5 to 1.0 is the approximate ratioat which turbulence becomes a problem. Furthermore, a decrease in the gas velocity creates the situation where there is not enough gas to effectively purge the lamp. Turbulence which is believed to be the cause of ineffectiveflushing is compounded by the use of spud 14 in prior art lamps as shown in FIG. 1. The purpose for having spud 14 extend into the lower portion of exhaust tube 15 is to prevent movement of the filament mount 19 during pinch sealing.

It is believed that when turbulence is created not all of the air and oxygen inside the envelope is flushed out or additional air is aspirated back into the envelope. The presence of air and or oxygen at high temperaturcs, such as those temperatures created by the fires used in pinch sealing, oxidize the lamp parts which make up filament mount 19. Oxidized parts lead to early lamp blackening and early lamp failure.

In an attempt to alleviate the oxidation problem, spud 14 was removed from the lamp design to allow a more even flow of flush gas. It was found that the oxidation problem, presumably associated with turbulence, although decreased, was still present to a significant degree. Additionally, the mount was no longer restrained and would tilt in one direction or other depending upon the flow of the molten quartz envelope during pinch sealing.

It is believed that the comparatively small inside length to inside diameter ratio, 3.5 or less, of the particular envelope continued to cause the turbulence because the flush gas would come through the exhaust tube at a velocity and pressure such that the gas would hit the mount pin and rebound in a direction back toward the exhaust tube. By comparison, if the envelope had a longer length, the flush gas velocity and pressure would be sufficiently dissipated and the gas could flow evenly out of the bottom of the envelope l7 and carry away any air or oxygen within the envelope.

Referring now to FIG. 2 of the drawing, a method of manufacturing lamp of the invention is therein illustrated. Lamp 25 is comprised of envelope 26 with attached exhaust tube 27, filament 28, short power conductor 29, long power conductor and wall bumper 31, FIG. 4. The filament along with the power conductors and wall bumper are generally referred to as a mount, 32. This mount is held in place by positioning the two power conductors 29 and 30 in mount pin 33.

With the envelope 26 and mount 32 positioned for pinch sealing, flush needle 34 is inserted through exhaust tube 27 and into envelope 26. It should be noted that the flush gas does not exit from the bottom of needle 34 but instead through ports 35 and 36 in a direction perpendicular to the axis of the envelope. It has been found that flushing the envelope in this manner diminishes the undesirable turbulence and in turn eliminates lamp part oxidation.

After the envelope is flushed, pinch jaws, not shown, press the heated lower end of the envelope to form pinch seal 37, FIG. 3. The flow of flush gas is terminated simultaneously with the formation of the pinch seal. Following this operation, the lamp is filled with a fill gas, which may contain a halogen to prevent bulb wall blackening, and the exhaust tube is tipped off. FIG. 3 shows the tipped-off residue as number 38.

During the pinch sealing process, mount 32 has a tendency to tilt depending upon which direction the mo]- ten quartz flows. Accordingly, a component, which does not interfere with the flow of flush gas, is needed to prevent this tilting. Such a component is wall bumper 31, FIG. 4, which is comprised ofa large outer wire turn 39 and a plurality of smaller wire turns 40 which are screwed onto helix 41 of power conductor 30.

The outside diameter of outer wire turn 39 is such that it is only slightly smaller than the inside diameter of envelope 26. Any movement of the mount 32 would move large power lead 30 and wall bumper 31. A slight movement of the bumper brings it in contact with the bulb wall and further tilting of the mount is restrained.

Another feature of the wall bumper is that it is unnec essary to insert any part of it into the exhaust tube as it was with the spud 14 of the prior art lamp illustrated in FIG. 1. Bumper 31 restrains movement through contact with the bulb wall and through contact with the exhaust tube wall. This allows for the unrestricted flow of gas through the envelope for purposes of removing any air or oxygen prior to elevating the temperature of the lamp parts from the pinch sealing fires.

By way of example only, the lamp illustrated in FIGS.

2 and 3 is a 600-watt, -volt tungsten-halogen lamp filled with nitrogen, 0.2% CH Br and 0.1% 0 at a pressure of L800 torr. The material used for the wall bumper is 0.01 2-inch diameter tungsten wire, the larger diameter turn has an outside diameter of 0.530 inch while the smaller turns have an inside diameter of 0.067 inch and have five turns, left-hand percent pitch. Envelope 26, called a TT5/2 with an outside diameter of l l/l6 inch, is made of quartz or high temperature glass and has an inside diameter of 0.59 1 inch and an inside length, measured from the dome radius to the bottom of the open envelope, of 1.57 inch.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A single-ended electric incandescent lamp comprising:

a tubular envelope of vitreous light-transmitting material having a pinched sea] at one end and a tipped off exhaust tube at the other;

a pair of spaced heavy rigid conductors of unequal length embedded in said pinch seal, each having an attached foil portion extending hermetically through said pinch seal to provide external connections;

the inner end of the shorter conductor terminating within said envelope in a spudded end close to the pinch-sealed end of said envelope;

the longer conductor extending longitudinally along a side wall of the envelope and terminating in turns tightly wrapped around an axial spud having a portion extending toward the pinch-sealed end of the lamp;

a coiled coil filament of refractory metal wire and substantially linear configuration fastened to and extending betweenthe spudded end of said shorter conductor and said spud;

and a coil support of relatively fine flexible wire having one end formed into a loop slightly smaller in diameter than the inside diameter of said envelope and the other end. formed into turns wrapped tightly over the turns of said longer conductor around said spud,

said support serving as a wall bumper to maintain the filament in place without obstructing the flow of flushing gas during the pinch sealing of said lamp and to absorb shocks and vibration during life of the lamp.

2. A lamp as in claim 1 wherein the length to diameter ratio of the envelope does not excess about 3.5 to l. 

1. A single-ended electric incandescent lamp comprising: a tubular envelope of vitreous light-transmitting material having a pinched seal at one end and a tipped off exhaust tube at the other; a pair of spaced heavy rigid conductors of unequal length embedded in said pinch seal, each having an attached foil portion extending hermetically through said pinch seal to provide external connections; the inner end of the shorter conductor terminating within said envelope in a spudded end close to the pinch-sealed end of said envelope; the longer conductor extending longitudinally along a side wall of the envelope and terminating in turns tightly wrapped around an axial spud having a portion extending toward the pinchsealed end of the lamp; a coiled coil filament of refractory metal wire and substantially linear configuration fastened to and extending between the spudded end of said shorter conductor and said spud; and a coil support of relatively fine flexible wire having one end formed into a loop slightly smaller in diameter than the inside diameter of said envelope and the other end formed into turns wrapped tightly over the turns of said longer conductor around said spud, said support serving as a wall bumper to maintain the filament in place without obstructing the flow of flushing gas during the pinch sealing of said lamp and to absorb shocks and vibration during life of the lamp.
 2. A lamp as in claim 1 wherein the length to diameter ratio of the envelope does not excess about 3.5 to
 1. 